A further comparison of radioassay results for serum and plasma

We evaluated results for serum vs. plasma for 12 selected radioassay procedures. Blood samples were collected with heparin, oxalate-fluoride, or ethylenediaminetetraacetate as anticoagulant and compared with the corresponding serum samples. In combination with a previous report [Kubasik, N.P., and Sine, H.E., Clin. Chem. 24 137 (1978)] we have now tested a total of 25 different analytes, using 31 manufacturers' kits. Differences were again demonstrated between serum and plasma that may be of sufficient magnitude to alter clinical interpretation of the results. Assays also demonstrated differences based on the procedure used.